Weeds are plants that compete with cultivated plants in an agronomic environment and cost farmers billions of dollars annually in crop losses and the expense of efforts to keep weeds under control. Weeds also serve as hosts for crop diseases and insect pests. Weeds are plants that are unwanted in any particular environment. The losses caused by weeds in agricultural production environments include decreases in crop yield, reduced crop quality, increased irrigation costs, increased harvesting costs, reduced land value, injury to livestock, and crop damage from insects and diseases harbored by the weeds. The principal means by which weeds cause these effects are: 1) competing with crop plants for water, nutrients, sunlight and other essentials for growth and development, 2) production of toxic or irritant chemicals that cause human or animal health problem, 3) production of immense quantities of seed or vegetative reproductive parts or both that contaminate agricultural products and perpetuate the species in agricultural lands, and 4) production on agricultural and nonagricultural lands of vast amounts of vegetation that must be disposed of Herbicide tolerant weeds are a problem with nearly all herbicides in use, there is a need to effectively manage these weeds. There are over 365 weed biotypes currently identified as being herbicide resistant to one or more herbicides by the Herbicide Resistance Action Committee (HRAC), the North American Herbicide Resistance Action Committee (NAHRAC), and the Weed Science Society of America (WSSA).
Sorghum weed species, especially, Johnsongrass (Sorghum halepense) shattercane (Sorghum bicolor) and sudangrass (Sorghum Sudanese) are difficult to control weeds that have been shown to develop tolerance to several classes of frequently used herbicides.
The present invention provides herbicidal compositions that comprise polynucleotide compositions useful for modulating gene expression in the Sorghum weed species, johnsongrass in particular, genes providing the production of herbicide target proteins, such as, acetyl-CoA carboxylase (ACCase), acetolactate synthase (ALS large subunit and ALS small subunit, also known as acetohydroxyacid synthase, AHAS), dihydropteroate synthetase (DHPS), 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), glutamine synthetase (GS2), 4-hydroxyphenyl-pyruvate-dioxygenase (HPPD), phytoene desaturase (PDS), protoporphyrinogen IX oxidase (PPDX) in plants for the purpose of enhancing control of johnsongrass in an agronomic environment and for the management of herbicide resistant johnsongrass.